I. Technical Field
The present invention relates to a method for fabricating a functional film and relates to, for example, a method for fabricating an organic electro-luminescence display (hereinafter, abbreviated as an organic EL display). More specifically, the present invention relates to a functional-film fabricating method including forming an organic light-emitting layer and the like using an ink jet apparatus.
II. Description of the Related Art
Organic EL displays are broadly divided into two types as follows, based on the method for forming organic light emitting layers. One type is a method which forms organic light-emitting layers through vapor deposition and is used in cases where the organic light-emitting layers are made of low molecular organic materials. The other type is a method which forms organic light-emitting layers through solvent coating methods and is used in cases where the organic light-emitting layers are made of low-molecular organic materials, as a matter of course, and also in cases where they are made of high-molecular organic materials.
As one of representative means for forming organic light-emitting layers through solvent coating methods, there is a method which forms an organic light-emitting layer by ejecting droplets of ink containing an organic light-emitting material to pixel areas on a display substrate to form an organic light-emitting layer, using an ink jet apparatus (refer to JP-A No. 2004-362818, for example). In this case, the ejected ink droplets contain an organic light-emitting material and a solvent.
General ink jet apparatuses include ink jet heads having plural nozzles and are adapted to eject ink from the nozzles while controlling the positional relationship between the nozzles in the ink jet heads and a substrate (refer to JP-A No. 2003-266669, for example). JP-A No. 2003-266669 discloses forming pixels having a predetermined line width, through spreads of droplets accreted on a substrate in isotropic directions.
In an ink jet apparatus, if a time interval for causing an ink jet head to eject droplets is interrupted only slightly (for example, an interruption of ejection for 60 seconds), a non-ejectable is induced and, further, even at a continuous ejection state, a non-ejectable nozzle may be induced in some cases. Therefore, in general, recovery processing for sucking ink from such non-ejectable nozzles and the like have been performed (refer to JP-A No. 2004-142422, for example). Further, there has been suggested a method which, in the event of occurrence of a non-ejectable nozzle, performs complementing for the areas to be originally subjected to recording through the non-ejectable nozzle, while keeping the non-ejectable nozzle as such (refer to JP-A No. 2000-284113 and JP-A No. 2005-67049, for example). JP-A No. 2000-284113 discloses a method which performs complementing for areas to be originally subjected to coating through non-ejectable nozzles, by displacing the positions of other nozzles. Further, JP-A No. 2005-67049 discloses an ink jet head including two nozzles parallelly arranged in the direction of scanning for use in applying a coating to the same areas and, further, suggests a method which, if one of the arranged nozzles becomes a non-ejectable nozzle, performs complementing using the other ejectable nozzle and, also, a method which, if both of the two nozzles are non-ejectable nozzles, performs complementing by applying a coating only to areas adjacent to the to-be-coated areas using an ejectable nozzle adjacent to non-ejectable nozzles. However, the ink jet head disclosed in JP-A No. 2005-67049 is a device for recording images formed from dot patterns on recording mediums such as paper sheets, plastic thin plates and the like. Thus, this ink jet head is different from an ink jet apparatus for use in functional-film fabricating methods for forming organic light-emitting layers, in terms of objects to be subjected to coating.
FIGS. 13A and 13B illustrate an example of an ink jet head disclosed in JP-A No. 2005-67049 and a result of recording on a recording medium as an object to be subjected to coating using the ink jet head. FIG. 13A illustrates the placement of ejectable nozzles and non-ejectable nozzles in the ink jet head. FIG. 13B illustrates the result of recording on a recording sheet 24 using the ink jet head illustrated in FIG. 13A. In FIG. 13A, a reference character 21 designates the ink jet head, a reference character 22 designates ejectable nozzles (diagonal-line circles) which eject ink, and a reference character 23 designates non-ejectable nozzles (white circles) eject no ink. In cases of applying a coating of ink to the recording sheet 24 using the ink jet head 21 having the two nozzles parallelly arranged as described above, there are formed areas 25 (diagonal-line circles) coated with a normal amount of droplets of the ink. If there are arranged nozzles both of which are non-ejectable nozzles, there are formed white-line areas 27 (white circles) induced by these non-ejectable nozzles, and also there are formed areas 26 (black circles) to which the ejectable nozzles adjacent to the white-line areas 27 have alternately applied a coating with a doubled amount of droplets. The ink jet head 21 disclosed in JP-A No. 2005-67049 is adapted to eject ink the recording sheet 24 as described above, in order to cause the non-ejected areas (the white-line areas 27), which are the areas of the recording sheet 24, and which can not be coated with the ink, to be visually inconspicuous.
The recovery operation disclosed in JP-A No. 2004-142422 is adapted to cover non-ejectable nozzles with caps and to suck ink from these non-ejectable nozzles. In order to perform this recovery operation, it has been necessary to perform recovery operations by covering the nozzles with the caps and, then, perform operations for removing the caps and for restoring the original droplet ejection state after the completion of the recovery operation. This has induced a time loss, which has been unpreferable in view of the productivity improvement. Further, in some cases, it has been impossible to completely recover non-ejectable nozzles, even by performing such recovery operations. Therefore, as a method for performing complementing without performing recovery operations on non-ejectable nozzles, there has been recording methods disclosed in JP-A No. 2000-284113 and JP-A No. 2005-67049 as described above, although these methods are different in terms of objects to be coated with ink.
The recording method disclosed in JP-A No. 2000-284113 is a method which performs complementing by re-scanning the areas to be originally coated through non-ejectable nozzles, while displacing the positions of other ejectable nozzles. This increases the number of scannings with the number of induced non-ejectable nozzles, which has been unpreferable in view of the productivity improvement.
Further, regarding the ink jet head including two nozzles arranged in the direction of scanning, which is disclosed in JP-A No. 2005-67049, there has been suggested a method which, if one of the arranged nozzles is a non-ejectable nozzle, performs complementing using the other ejectable nozzle and, if both of the arranged nozzles are non-ejectable nozzles, performs complementing using an adjacent ejectable nozzle. In cases where both the arranged two nozzles are non-ejectable nozzles and an ejectable nozzle adjacent thereto is used for complementing, the amount of launched droplets is increased at the same position, without changing the position of this adjacent ejectable nozzle. In cases of using this recording method for a functional-film fabrication method, the amount of ink droplets is increased at the same position and, in cases where the respective coating areas for R (red), G (green) and B (blue) are arranged, for example, there is a high possibility that the ink intrudes into the adjacent areas and color mixing occurs, due to the vibration caused by the accretion of droplets and the error of droplet shot accretion positions. Further, in the event of occurrence of continuous two or more non-ejectable nozzles, out of the nozzles arranged in the direction orthogonal to the direction of scanning, the number of droplets is increased at the same position, which degrades the film uniformity, thereby inducing the problem of difficulty of performing predetermined complementing.
The present invention was made in view of the problems induced in formation of functional films using conventional ink jet apparatuses and aims at providing a functional-film fabricating method capable of certainly forming uniform functional films without degrading the productivity, in the event of occurrence of continuous two or more non-ejectable nozzles, out of nozzles in an ink jet apparatus.